Risk Assessment of "Other Substances" – L-alanine

ABSTRACT

The Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) has, at the request of the Norwegian Food Safety Authority (Mattilsynet; NFSA), assessed the risk of "other substances" in food supplements and energy drinks sold in Norway. VKM has assessed the risk of doses given by NFSA. These risk assessments will provide NFSA with the scientific basis while regulating "other substances" in food supplements. "Other substances" are described in the food supplement directive 2002/46/EC as substances other than vitamins or minerals that have a nutritional and/ or physiological e ffect . It is added mainly to food supplements, but also to energy drinks and other foods. In this series of risk assessments of "other substances" the VKM has not evaluated any claimed beneficial effects from these substances, only possible adverse effects. For the current report VKM has studied previous risk assessments and performed two systematic literature searches for any published studies assessing negative health effects of L-alanine in humans or animals. According to information from NFSA, L-alanine is an ingredient in food supplements sold in Norway. NSFA has requested a risk assessment of L-alanine 3500, 3750, 4000, 4250 and 4500 mg/day. Foods rich in alanine are generally protein rich foods such as meat, dairy products, legumes, fish, nuts, seeds, eggs and whole grains. Based on NHANES III (19881994), the overall mean intake of L-alanine from food and food supplements in the United States was 3.6 g/day. L-alanine is a naturally occurring non-essential α-amino acid belonging to the group of the 20 amino acids that are normal components of food proteins. L-alanine acts as an intermediary between protein catabolism and carbohydrate synthesis. It can be easily synthesised from the alpha keto acid pyruvate and has close links to several metabolic pathways including glycolysis, gluconeogenesis, and the citric acid cycle. Together with lactate it is capable of generating glucose from muscle protein through gluconeogenesis in the liver. Alanine thus plays a central role in the metabolism of muscle protein and is a key factor in nitrogen metabolism. Previous reports from the US Institute of Medicine (IOM) 2005, the French Food Safety Agency (AFSSA) 2007 and the Spanish Agency for Food Safety and Nutrition (AESAN) 2012 did not conclude regarding safe doses of L-alanine, but stated that data on adverse effects of L-alanine intake from supplements were not sufficient for a dose-response assessment and establishment of a tolerable upper intake level. Few studies have assessed health effects of L-alanine supplementation in humans, and these were generally not designed to evaluate potential harmful effects of L-alanine. Most human experimental studies gave single doses (up to 50 g) or short-term loading doses (e.g. 25 to 45 g/hour during exercise) to study metabolic responses such as ergogenic effects during exercise or prevention of ketosis after fasting. Adverse health effects were not reported except for abdominal discomfort and stomach cramps, nausea and diarrhea after consuming high doses. No studies assessed long-term effects of L-alanine supplementation, and no studies gave doses comparable to the doses under consideration in the present report. Only one dose-reponse toxicity study in rodents has been found (Chow et al., 1976). In that study, growing Wistar rats were fed up to 20% DL-alanine (a racemic mixture of D- and Lalanine) in their basal diet for 26 weeks, with no effect on liver and kidney weight and no pathological changes in any organs. The study was taken into account due to the otherwise scarce literature on L-alanine toxicity, and could be used since there were no adverse effects at the highest dose tested. The no observed adverse effect level (NOAEL) in mg L-alanine per kg body weight per day was not stated. VKM has therefore estimated the NOAEL using information about average reported feed consumption and average body weights of the animals, and divided by 2 to obtain a NOAEL for L-alanine, arriving at approximately 6450 mg/kg bw/day in male rats and 9700 mg/kg bw/day in female rats. A standard toxicological approach dividing by an uncertainty factor (UF) of 10 for between-species variation and an additional UF of 10 for within-species variation gives the value of 64.5 mg/kg bw per day in females and 97.0 mg/kg bw per day in males, corresponding to approximately 4500 mg/day and 6800 mg/day for a 70 kg man and woman, respectively. VKM also calculated the margins of exposure (MOE) between the estimated NOAEL and the estimated daily exposures from the five supplement doses given by the NFSA (based on default average body weights for the age groups). MOE were 100 or higher for all five doses in adults. For adolescents 14 to <18 years, the MOE was 88 for the highest dose under consideration. For children 10 to <14 years, MOE ranged from 62 for the highest dose to 80 for the lowest dose. The VKM considers that these margins are relatively high and are acceptable based on the following considerations The highest dose tested in growing rats did not cause adverse effects, implying that the “true” NOAEL is unknown and could be considerably higher. Furthermore, L-alanine is a nutrient participating in normal energy metabolism as a substrate for glucose. It is consumed in the magnitude of 3 to 4 g/day on average in the habitual diet, and it has not been associated with harmful effects in humans beyond gastrointestinal effects when consuming very high single doses (50 g, or at a consumption rate of 30 to 45 grams per hour during exercise). VKM concludes that In adults (≥18 years), the specified doses 3500, 3750, 4000, 4250 and 4500 mg/day L-alanine in food supplements are unlikely to cause adverse health effects. In adolescents (14 to <18 years), the specified doses 3500, 3750, 4000, 4250 and 4500 mg/day L-alanine in food supplements are unlikely to cause adverse health effects. In children (10 to <14 years), the specified doses 3500, 3750, 4000, 4250 and 4500 mg/day L-alanine in food supplements are unlikely to cause adverse health effects. Children younger than 10 years were not within the scope of the present risk assessment.